The present invention relates to a method for transferring a nucleic acid, a derivative or an analogue thereof across a biological membrane, and/or directing it to a specific location within or on a cell, by use of a novel synthetic transport entity.
Methods for genetic modification, wherein exogenous genetic material is introduced into host cells to provide a function thereof, are usually limited by the rate of the uptake of the genetic material introduced into the cells. In eucaryotic cells, the nuclear uptake is often limiting. Even though direct injection methods have been used in this context, they are, however, extremely slow and labor-intensive. Thus, for use in larger scales, standard methods for transferring nucleic acids into cells are rather based on an uptake of complexes formed between different chemical compounds of nucleic acids. The genetic material is then left to enter the nuclei of the cells passively.
Nuclear localization signals (NLS) have been proposed in this context. As one example, Sebestyen et al. (Nat. Biotechnol, 1998, January; 16:(1):80-85) have suggested to use digitonin permeabilized cells to enable nuclear translocation after chemically linking an NLS peptide to a plasmid.
Further, Yoneda et al. (Exp. Cell. Res. 201:213 (1992)) have reported translocation of proteins larger than 970 kDa into the nucleus. More specifically, a fusion protein containing a nuclear localization signal (NLS) is transported into the nucleus of a cell.
U.S. Pat. No. 5,539,082, in the name of Nielsen et al, discloses a class of compounds known as peptide nucleic acids (PNAs). The PNAs described therein may comprise ligands, such as DNA bases, conjugated to a peptide backbone through a suitable linker. The PNAs according to U.S. Pat. No. 5,539,082 may e.g. be exploited to target specific genes and viruses within a cell, while the properties thereof are characterised by an absence of charge and a water solubility.
Further, WO 96/11205, also in the name of Nielsen et al, proposes a PNA conjugate comprised of a PNA chemically bound to a conjugate, such as any one of a large number of molecules, all of which are aimed at providing the PNA with desired properties. Accordingly, the PNA is useful as such, for example as a diagnostic or therapeutic agent. Said PNA is, similar to the above discussed U.S. Pat. No. 5,539,082, intended for exerting its advantageous functions within a cell.
The object of the present invention is to provide a general and efficient method of genetic modification, wherein a nucleic acid of interest, a derivative or an analogue thereof is transferred across a biological membrane, and/or directed to a specific location within or on a cell, by a novel synthetic transport entity. The present transport entity is according to the invention provided by coupling a functional entity (FE), which may represent any kind of desired biological property, to a binding element (BE), such as a peptide nucleic acid (PNA), optionally with a linker molecule for keeping said FE and BE apart; and hybridisation thereof to a BE target present on a carrier of the nucleic acid of interest. The invention also relates to the novel transport entity as such as well as to various advantageous uses thereof.